Surface inspection is important in a broad range of fields, including manufacturing. A common goal of surface inspection is to detect surface defects or irregularities of an imaged object. Surface inspection may be carried out manually or by automatic processes.
Specular surfaces are especially difficult to manually inspect for visual defects. Automated methods of specular surface inspection may consist of employing deflectometry techniques, which may require a target object—regardless of specularity—to be motionless for a certain time period, such as more than ten seconds, while a known light pattern is projected upon the surface. Currently the sensing system (i.e. camera or other optical sensor) must grab a sufficient number of frames of the object in full view to accurately perform geometry based imaging. Without this, these systems may suffer from perspective deformation.
In the manufacturing context, inaccurate inspection leads to wasted product, wasted time and adds to manufacturing inefficiencies. Manufacturing environments, including automotive processes are prone to surface defects. For example, paint processes encounter numerous paint defects such as paint sags, dirt, spits and ‘orange peeling’—regardless of precautions taken to ensure the cleanliness of the painting area. Defects on the painted surface of a vehicle are not acceptable to consumers. Paint inspection of a full vehicle requires extensive human inspection which may be prone to human error. Automated methods of specular surface inspection may be used, whereby a vehicle may be required to be stationary for ten seconds or more during imaging. This can be disruptive to the flow of the vehicles through a manufacturing plant, affect production output and require particular staffing and maintenance requirements. Additionally, most current specular imaging systems require that the location of any defect be known relative to the geometry of a car, which may necessitate the use of computer-aided drafting (“CAD”) models.